The present invention relates to a testing apparatus for vehicle axles, wheel suspensions, and similar structures. For testing such structural components it is desirable to introduce several forces or force components which are effective in different directions, for example, in the vertical direction, the longitudinal direction, and in the lateral direction. The longitudinal direction in this context would be the direction of vehicle movement, whereas the lateral direction would be in the direction of the longitudinal axis of the vehicle axle. These forces are applied by force applying means including force introducing elements, actuating elements and force transmitting elements. The force applying means may be connected to the respective test sample in a rigid manner or in a rotatable manner. Further, the force applying means are effective at least in one force introducing point of a force introducing element.
In the testing of vehicle axles and wheel suspensions, it is necessary that the forces and loads which occur in the actual operation of the vehicle are simulated as close to actuality as possible and that the simulated forces are applied to the test sample also substantially in the same manner as happens in the operation of the vehicle. The forces to be simulated result normally from the forces which occur in the point of contact between the vehicle wheel and the road surface. These forces involve, in addition to the force resulting from the vehicle weight and load, which is effective in the vertical direction, the horizontal breaking forces and acceleration forces extending in the plane defined by the vehicle wheel. These forces further involve longitudinal and vertical forces resulting from holes and bumps in the road surface, as well as lateral forces extending substantially perpendicularly to the plane of the vehicle wheel. Such lateral forces may, for example, be effective on the vehicle wheel when the vehicle negotiates a curve.
The forces to be simulated by the testing apparatus are normally generated by hydraulic load piston cylinder devices which are connected to the test sample by means of suitable linkage and force introducing elements. The force introducing elements may be secured in a rotatable manner to the vehicle axle, whereby no torque moments may be applied to the axle. The force introducing elements may also be connected to the vehicle axle in a rigid manner, whereby force components effective perpendicularly to the vehicle axle result in respective torque moments. It is possible to simulate any desired loads, especially also dynamic loads, by means of servo-hydraulic control and regulating devices. Reference is made in this context to a prior art article entitled "Multi-Axial Servo Hydraulic Testing Devices For Vibration Strength Investigations On Motor Vehicle Axles", published in ATZ (Automobiltechnische Zeitschrift), Volume 4, 1972, pages 139-145, by Friedrich Klinger and Rolf Ross.
For the complete simulation of all essential forces and moments which may occur on a vehicle wheel the following force components are necessary:
(1) a vertical force, PA1 (2) a longitudinal force effective at a point on the circumference of the wheel, PA1 (3) a lateral force effective at a point on the circumference of the wheel, and PA1 (4) a longitudinal force effective at the axial stud or journal.
However, heretofore it was deemed to be satisfactory that only three forces or rather, force components, are simulated on testing devices for vehicle axles. This has been found to be inadequate. Especially in connection with axles which are subject to a steering, additional difficulties occur because the structural components to which the testing forces must be applied are constructed so as to be tiltable for following any steering motions. The difficulty arises from the fact that the actuating elements for introducing the testing forces must not hinder the steering motion. Further difficulties occur if it becomes necessary to test the vehicle axles or wheel suspensions in the installed condition in the vehicle because in this environment the chassis components or vehicle body components may interfere with the installation of the load cylinders and the actuating linkage members.